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**Hank Jarrett** · 07-22-2006, 05:43

Re: Locating center of an outlined 3/16" hole?

Mike, What you are looking for is what I used to call a" hole locator" (I know there are a BUNCH of names for it). It looks like a "C" clamp with tubes on the jaws. The tubes are welded on the "C" in one piece and a gap cut in after everything is cooled. This way there are two tubes in a straight line. You just need to slip your inner tube into the outer one, put a drill bit in one side of the tool and fit it into the outer tube cross hole to align the tool to the holes. Then just drill through the other side with a hand drill using the outer tube hole as a guide. It's fast, easy and accurate. You don't need a laithe or a drill press.
I know this explination isn't great but give me a call and maybe I can explain it better. I have used these things for years. The NADEP used to make them for a job then throw them away.
Hank

**mhorowit** · 07-22-2006, 13:32

Re: Locating center of an outlined 3/16" hole?

Hank – let me recap to see if I’ve got what you’re saying:
- get a piece of tubing the size of the outer tube.
- Drill a 3/16” hole thru both walls of the tube.
- Clamp the tubing in a ‘C’ clamp with the drilled holes running parallel to the clamp screw. Weld the tube to the clamp – one side to the anvil, the other side to the moving part.
- Saw the tube lengthwise.

Don't we still have the problem of not knowing where to center the ‘tool’? Unless you are centering the tool over the scribed circle I mention in my initial post. Also, how do you assure yourself you are holding the hand drill at 90 degrees? Finally, what about a pilot hole, or are you suggesting the walls of the tubing are sufficient?

This is first cousin to the device used to drill a cotter-pin hole in a bolt, right?

– Mike

**VictorBravo** · 07-22-2006, 16:11

Re: Locating center of an outlined 3/16" hole?

Mike, try a drill bushing with the end relieved to sit on top of the inner tube. Make it from thick wall tubing, for a smaller pilot drill size, then drill it out to the same size as the hole. See attached rough sketch.

Attached Files

**mhorowit** · 07-22-2006, 23:34

Re: Locating center of an outlined 3/16" hole?

Bill - the problem is not one of drilling 90 degrees to the tube; it's being able to locate the hole around the diameter of the tube to be drilled. By 'locate' I mean figuring where the pin-prick is made. I know the hole is .750 from the end of the tubing and by 0730 I will have put the parts together and 'scribed' the outline of the hole in the part to be drilled; however, I still need to accurately locate the center of that circle to make the centerpunch.

- MIke

**VictorBravo** · 07-23-2006, 01:10

Re: Locating center of an outlined 3/16" hole?

My method will do what you are trying to do. If you substitute the word "pilot drill" for "pinprick", you will see what I am talking about. The "drill bushing" I drew roughly actually fits exactly inside the diameter of the outer tube hole... so the pilot drill going through the bushing marks the center of the outer hole. Once the first side hole is drilled, put a tight fitting pin through inner and outer tube to keep everything aligned, put the drill bushing in the opposite hole in the outer tube, and locate the center of the other hole.

So, if the hole in your outer piece of tubing is 3/16, then the OD of the drill bushing is also 3/16 minus a thousandth for clearance. Assuming the wall thickness is constant for the bushing, when you run the drill through the bushing it will drill through the geometric center of the hole and drill a pilot through the right location in the inner tube.

Capish?

**mhorowit** · 07-23-2006, 05:04

Re: Locating center of an outlined 3/16" hole?

Originally posted by VictorBravo

Capish?

verstain - Mike

**Hank Jarrett** · 07-23-2006, 06:11

Re: Locating center of an outlined 3/16" hole?

OK, I was afraid my explination wasn't quite clear enough.
Picture a piece of steel shaped like a "D". The curved part of the "D" is sheet metal and the "I" part is a tube welded to it with an ID to match your drilled hole in your outer tube. Once it is welded to the curved (or "C" part) you can cut the middle out of the tube and the two pieces are still in alignment.
You put one of these stubs up to the hole in your outer tube and slip a drill shank in to align it with the drill hole in one side of your tube. The other tube of your tool now points directly at the first. When you put your drill in the other side and the point into the opposite drill hole in your drilled outer tube you have your drill held perfect to drill the INNER tube so that the holes in the outer and inner tubes are perfectly aligned. DON'T try and drill both sides and just push your alignment drill out the other side. Just take the tool and flip it over to do the other drilled hole.
If this still isn't clear let's get on the phone. If I had a photo of one of the tools it would be really clear (I need to work on my discriptions). I guess the tool isn't as widely used as I thought. Everybody around here seems to have a drawer full of them.

**jdoran** · 07-23-2006, 07:37

Re: Locating center of an outlined 3/16" hole?

Mike,

You seem to like gadgets,sooooooo-here's a solution for $40

Shop Tools, Grills, Clothing, Windows & Doors | Hartville Hardware

http://www.hartvilletool.com/product/11122

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John

**mhorowit** · 07-23-2006, 07:54

Re: Locating center of an outlined 3/16" hole?

Originally posted by Hank Jarrett

OK, I was afraid my explination wasn't quite clear enough.
Picture a piece of steel shaped like a "D". The curved part of the "D" is sheet metal and the "I" part is a tube welded to it with an ID to match your drilled hole in your outer tube. Once it is welded to the curved (or "C" part) you can cut the middle out of the tube and the two pieces are still in alignment.
You put one of these stubs up to the hole in your outer tube and slip a drill shank in to align it with the drill hole in one side of your tube. The other tube of your tool now points directly at the first. When you put your drill in the other side and the point into the opposite drill hole in your drilled outer tube you have your drill held perfect to drill the INNER tube so that the holes in the outer and inner tubes are perfectly aligned. DON'T try and drill both sides and just push your alignment drill out the other side. Just take the tool and flip it over to do the other drilled hole.
If this still isn't clear let's get on the phone. If I had a photo of one of the tools it would be really clear (I need to work on my discriptions). I guess the tool isn't as widely used as I thought. Everybody around here seems to have a drawer full of them.

Hank - if you don't have a scanner, you can use MS PAint to draw a .bmp - Mike

**mhorowit** · 07-23-2006, 09:59

Solution: Locating center of an outlined 3/16" hole?

It turned out I was able to use the existing hole in the outer tube as a guide.

Here's what I did: built a punch from 3/16" rod (see attached).
Drilled a pilot hole in a piece of tubing just able to slip over the target tubing.
(NOTE: in the real case, the 3/16" hole in the outer tube already exists; this exercise was done using scrap tubing). The walls of the hole in the larger tube act as a guide.
Blacken the target tube.
Slip the punch in place.
Gentle tap and a small mark is made in the target tube.
A prick punch catches in the mark, followed by a center punch. Hurrah!!

Making the 15* taper in the punch: chuck the rod in the drill press. Tilt the table to 15*. Clamp a thin piece of wood to the table (so a file won't scratch the table). Lay the file on the wood. Turn on the drillpress, bring the work down to the file and very gently push the file into the work. Repeat. WARNING: if you apply too much pressure to the file (from the press), it tends to push out the file towards the operator. No, I didn't discover this accidently - you can feel the file reacting to the rotation of the chuck.

Why 15*? First angle I came to that made a mark on the target tubing. I was concerned that if the angle were too great, I would reduce the diameter of the punch. For the thickness of the outer tube I probably could have made a more acute angle.

- MIke

Attached Files

**Hank Jarrett** · 07-23-2006, 12:47

Re: Locating center of an outlined 3/16" hole?

Hope this attaches OK. The guide pin is on the left going through the outer tube. The drill is going in from the right and has already drilled the match hole in the inner tube. Now just flip it over and drill the other side with the guide pin (I use a second drill bit) through both tubes to hold everything in alignment.
Hank

**Hank Jarrett** · 07-23-2006, 12:52

Re: Locating center of an outlined 3/16" hole?

Alright, the stinking attachment didn't. I HATE computers! How many times have people told how to attach an image and I still get it wrong! @$#%(&(*!!
STUPID THING STILL WON'T UPLOAD!! Just send me your email and I'll send it direct. At least I won't be embarrassed by my rotten drawing talent on the group.
Hank (;f

Yea, I REALLY DO feel like a weed is growing out of the top of my head.

**mhorowit** · 07-23-2006, 15:18

Re: Locating center of an outlined 3/16" hole?

LOL

OK, we'll have to recognized some of the tribe may be computer impared.
Others of us need to recognize the diameter of a tube includes two wall thicknesses

My addy is [email protected]

- MIke

**mgold** · 07-23-2006, 21:23

Re: Locating center of an outlined 3/16" hole?

just a thought take a 3/16 wood dowell and make your cross arrows
on the end. then sharp it like to a point then put a touch of paint on the
end and put in the hole. then center punch it. just a thought

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Locating center of an outlined 3/16" hole?

Locating center of an outlined 3/16" hole?

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